This study aimed to evaluate the gas exchanges and photosynthetic pigments of soursop seedlings cv. 'Morada Nova' irrigated with saline waters and subjected to exogenous application of hydrogen peroxide by seed soaking and foliar spraying. The study was carried out using plastic bags under greenhouse conditions at the Center of Technology and Natural Resources of the Federal University of Campina Grande, PB, Brazil, using a eutrophic Regolithic Neosol of sandy loam texture. Treatments were arranged in a randomized block design, in 5 x 5 factorial scheme, which consisted of five levels of electrical conductivity -ECw (0.7; 1.4; 2.1; 2.8 and 3.5 dS m -1 ) of irrigation water and five concentrations of hydrogen peroxide -H 2 O 2 (0, 25, 50, 75 and 100 µM), with four replicates and three plants per plot. As the salt stress increased, there were reductions in internal CO 2 concentration, instantaneous carboxylation efficiency and water use efficiency, and instantaneous carboxylation efficiency was the most sensitive variable. Hydrogen peroxide at concentrations of 25 and 50 µM attenuated the deleterious effects of water salinity on stomatal conductance, CO 2 assimilation rate and chlorophyll a content, and the concentration of 25 µM was the most efficient. The content of chlorophyll b and carotenoids of soursop cv. 'Morada Nova' had the deleterious effects caused by the salinity of irrigation water mitigated by the exogenous application of hydrogen peroxide in the concentration of 25 μM.Estresse salino e aplicação exógena de peróxido de hidrogênio nos parâmetros fotossintéticos da gravioleira RESUMO: Objetivou-se com este trabalho avaliar as trocas gasosas e os pigmentos fotossintéticos de mudas de gravioleira cv. Morada Nova irrigadas com águas salinas e submetidas à aplicação exógena de peróxido de hidrogênio via embebição das sementes e pulverizações foliares. O estudo foi conduzido em sacolas plásticas sob condições de casa de vegetação pertencente ao Centro de Tecnologia e Recursos Naturais da Universidade Federal de Campina Grande, PB, utilizando-se um Neossolo Regolítico Eutrófico de textura franco-arenosa. Os tratamentos foram distribuídos no delineamento de blocos casualizados, em arranjo fatorial 5 x 5, sendo cinco níveis de condutividade elétrica da água de irrigação -CEa (0,7; 1,4; 2,1; 2,8 e 3,5 dS m -1 ) e cinco concentrações de peróxido de hidrogênio -H 2 O 2 (0, 25, 50, 75 e 100 µM), com quatro repetições e três plantas por parcela. Com o aumento do estresse salino, ocorreu diminuição na concentração interna de CO 2 , na eficiência instantânea da carboxilação e na eficiência no uso da água, sendo a eficiência instantânea da carboxilação a variável mais sensível. O peróxido de hidrogênio nas concentrações de 25 e 50 µM atenuou os efeitos deletérios da salinidade da água sobre a condutância estomática, taxa de assimilação de CO 2 e no teor de clorofila a, sendo a concentração de 25 µM a mais eficiente. O teor de clorofila b e carotenóides da gravioleira cv. Morada Nova teve os efeitos deletérios causados...

The semi-arid region of the Brazilian Northeast has adequate edaphoclimatic conditions for the passion fruit production, but the water used for irrigation commonly has high concentrations of salts that are harmful to the plant growth and development. A previous supply of hydrogen peroxide induces the acclimation of plants under saline stress conditions, reducing deleterious effects on their growth and physiology. This study aimed to evaluate the gas exchanges and growth of passion fruit as a function of irrigation with saline water and exogenous application of hydrogen peroxide. The experiment was carried out under greenhouse conditions, using a randomized block design, in a 4 x 4 factorial arrangement, being four levels of irrigation water electrical conductivity (0.7 dS m-1, 1.4 dS m-1, 2.1 dS m-1 and 2.8 dS m-1) and four hydrogen peroxide concentrations (0 µM, 25 µM, 50 µM and 75 µM), with four replicates and two plants per plot. The hydrogen peroxide application attenuated the deleterious effects of the irrigation water salinity on transpiration, CO2 assimilation rate, internal carbon concentration, plant height and leaf area of yellow passion fruit, at 60 days after sowing, with the concentration of 25 µM being the most efficient. Irrigation using water with electrical conductivity above 0.7 dS m-1 negatively affects the gas exchanges and growth of passion fruit, being the stomatal conductance and leaf area the most sensitive variables to the salt stress.

The search for alternatives that enable the use of saline waters in agriculture has become constant. In this context, the objective was to evaluate the effects of salicylic acid in mitigating salt stress effects on the growth and gas exchange of soursop cv. ‘Morada Nova’. The study was conducted in a greenhouse, in the municipality of Campina Grande - PB, Brazil. Treatments were distributed in randomized blocks, in a 5 x 4 factorial arrangement, corresponding to five levels of electrical conductivity of irrigation water - ECw (0.8; 1.6; 2.4; 3.2 and 4.0 dS m-1) and four concentrations of salicylic acid - SA (0; 1.2; 2.4 and 3.6 mM), with three replicates. Irrigation with saline water compromised the growth and gas exchange of soursop cv. ‘Morada Nova’. However, exogenous application of salicylic acid induced tolerance to salt stress in soursop plants, as their growth, transpiration, stomatal conductance, photosynthesis and instantaneous carboxylation efficiency were favored by the application of salicylic acid, even when exposed to water salinity.

The cultivation of irrigated soursop in semiarid Northeastern Brazil highlights the need for information regarding its responses to the salinity of irrigation water and the use of techniques that allow its exploration, such as the use of hydrogen peroxide. Thus, the study aimed to evaluate the effect of soaking of seeds and foliar application of hydrogen peroxide on soursop plant growth and physiology under conditions of salt stress. The study was conducted in lysimeters in a greenhouse, and the treatments were distributed in a randomized block design and 4 × 4 factorial scheme, with four values of electrical conductivity of the irrigation water - ECw (0.7, 1.7, 2.7, and 3.7 dS m-1) and four concentrations of H2O2 (0, 25, 50, and 75 μM), with three replicates and one plant per plot. H2O2 concentrations were applied via seed imbibition and foliar spray. Irrigation with water from 0.7 dS m-1 impairs gas exchange and absolute growth rates of plant height and stem diameter and relative growth rate in height of soursop plants. Concentrations of 35, 33 and 23 µM of hydrogen peroxide favored the relative and absolute growth rates of plant height and transpiration, respectively. Compared to the aerial part, the root of soursop plants is more affected when irrigated with water from 1.6 dS m-1.

The objective of this study was to evaluate the quantum yield and concentrations of photosynthetic pigments of naturally colored cotton genotypes under irrigation with waters of different electrical conductivities and foliar applications of hydrogen peroxide. The design used was randomized blocks in a 4 × 3 × 2 factorial arrangement, corresponding to four concentrations of hydrogen peroxide - H2O2 (0, 25, 50 and 75 μM), three genotypes of colored fiber cotton (‘BRS Rubi’, ‘BRS Topázio’ and ‘BRS Verde’) and two values of electrical conductivity of water (0.8 and 5.3 dS m-1), with three replicates. Irrigation with water of 5.3 dS m-1 reduces the chlorophyll a, chlorophyll b and total chlorophyll concentrations of ‘BRS Rubi’ cotton. The concentrations of photosynthetic pigments, maximum fluorescence, variable fluorescence and quantum efficiency of photosystem II of ‘BRS Rubi’ cotton increased under irrigation with 0.8 dS m-1 water and foliar application of 50 μM of hydrogen peroxide. Water of 5.3 dS m-1 and foliar applications of 75 μM of hydrogen peroxide reduce the concentrations of photosynthetic pigments, but did not cause damage to the efficiency of photosystem II of the colored cotton genotypes.